all: refactor router code to use interface

So the code is more modular, easier to read/maintain.

internal/router/synology/synology.go

@@ -0,0 +1,88 @@
+package synology
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+
+	"github.com/Control-D-Inc/ctrld/internal/router/dnsmasq"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/kardianos/service"
+)
+
+const (
+	Name = "synology"
+
+	synologyDNSMasqConfigPath = "/etc/dhcpd/dhcpd-zzz-ctrld.conf"
+	synologyDhcpdInfoPath     = "/etc/dhcpd/dhcpd-zzz-ctrld.info"
+)
+
+type Synology struct {
+	cfg *ctrld.Config
+}
+
+// New returns a router.Router for configuring/setup/run ctrld on Ubios routers.
+func New(cfg *ctrld.Config) *Synology {
+	return &Synology{cfg: cfg}
+}
+
+func (s *Synology) ConfigureService(config *service.Config) error {
+	return nil
+}
+
+func (s *Synology) Install(_ *service.Config) error {
+	return nil
+}
+
+func (s *Synology) Uninstall(_ *service.Config) error {
+	return nil
+}
+
+func (s *Synology) PreRun() error {
+	return nil
+}
+
+func (s *Synology) Configure() error {
+	s.cfg.Listener["0"].IP = "127.0.0.1"
+	s.cfg.Listener["0"].Port = 5354
+	return nil
+}
+
+func (s *Synology) Setup() error {
+	data, err := dnsmasq.ConfTmpl(dnsmasq.ConfigContentTmpl, s.cfg)
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(synologyDNSMasqConfigPath, []byte(data), 0600); err != nil {
+		return err
+	}
+	if err := os.WriteFile(synologyDhcpdInfoPath, []byte(`enable="yes"`), 0600); err != nil {
+		return err
+	}
+	if err := restartDNSMasq(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *Synology) Cleanup() error {
+	// Remove the custom config files.
+	for _, f := range []string{synologyDNSMasqConfigPath, synologyDhcpdInfoPath} {
+		if err := os.Remove(f); err != nil {
+			return err
+		}
+	}
+	// Restart dnsmasq service.
+	if err := restartDNSMasq(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func restartDNSMasq() error {
+	if out, err := exec.Command("/etc/rc.network", "nat-restart-dhcp").CombinedOutput(); err != nil {
+		return fmt.Errorf("synologyRestartDNSMasq: %s - %w", string(out), err)
+	}
+	return nil
+}